Field of the Invention
The present invention relates to the design of levitating magnetic bearings of the annular or conical-annular configuration, and more specifically, it relates to the use of alternative polarization and Amperian current directions in levitating passive magnetic bearing configurations.
Description of Related Art
Levitating magnetic bearings of the annular or conical-annular configuration are typically made using rectangular blocks that are assembled in a ring the radius of which is large compared to the dimensions of the bars so that the gaps at the outer edge are small compared to their dimensions. Key elements in the passive magnetic bearing systems developed at Lawrence Livermore National Laboratory (LLNL) are the permanent-magnet arrays that levitate the rotating system, e.g., the rotor of a flywheel energy storage system (EMB). It is therefore of value to consider designs of these systems that minimize the amount of magnet material required (reduces the weight added to the rotor), and reduce the material cost of the bearing, both from reducing the amount of permanent magnet material required to fabricate the bearing and/or to allow the use of less expensive magnet material. For example, the high-field permanent magnet material such as SmCo (Br=1.3 Tesla) and NdFeB (Br=1.4 Tesla) are very expensive ($100/lb for SmCo and $50/lb for NdFeB). Ferrite magnets (Br=0.4 Tesla) cost only $2/lb, and are also non-conducting, so that eddy-current losses are zero. New designs are desirable that improve the lift per unit area of levitating bearings, as compared to former designs, sufficiently as to allow the use of ferrite magnets for levitation of EMBs rotors in most cases. The present invention provides such designs